Introduction: LED Projector Mod for 3D Printing
This 'ible is based on the Pyle Audio PRJG45. The particular model you are working on may differ greatly from this one but if it's an LED projector then the basic process should be similar enough to follow.
I want to build a resin printer. I went shopping for a DLP projector and bought the Pyle Audio PRJG45, not realizing at the time that I had ordered an LED projector. Oops... Well, it projects with LEDs, and I already knew UV LEDs were available, so, how hard could it be to mod? Turns out, really easy.... except that it won't work the way I wanted it to.
I had planned to replace the white LED with a UV LED. Problem is, these LED projectors use an LCD to tint the white light and form pixels, and LCDs don't let UV light pass through them. LCD displays only let through select color ranges and UV light falls outside of that. All is not lost however as Resin is available which cures in other wavelengths than that which defines the ultra-violet range, for instance, blue light curing (~460nm) resin.
The instructions that follow were written for replacing the original white LED with a UV LED, which I now understand will not work due to the limitations of the LCD screen!
My current plan for this project is to 1. Replace the current LED with a blue LED (not sure what wavelength just yet) and 2. to acquire and experiment with blue light curing resin... of course the specifics there may change as I haven't worked it all out yet. I'll update this 'ible soon with corrected instructions and a section on the science behind why the UV LED won't work as planned and options to work around that. I also plan to acquire and hack a dead-bulb DLP projector with a UV LED replacement, providing me with a system for the more traditional printing resins, which I will also create an 'ible for.
This is an LED based light/image projector. The mod should be as simple as opening the machine up, de-soldering an LED and soldering in a replacement. There are a few details to work out along the way but I'll cover those in the next few steps.
- Soldering Iron
(I recommend at least an adjustable 60 watt iron like the one I linked to here.)
- Solder wiper pad or wire scrubber pad (yes, this works)
- A nice bright lamp or light source
(I use a small arm lamp with an LED bulb)
- Tiny Screwdriver
(Precision size with 4 inch long shaft, minimum.)
- Solder Sucker or de-soldering braid
- Grounding pad and or strap
(You may be able to do without these but why take a chance?)
- A little patience
A 10 watt LED of the wavelength that you desire to work with.
(Make sure you can acquire or prepare resin that cures in that wavelength before you purchase the LED)
Let's get started!
Step 1: Taking the Top Off
The 'lid' of the projector is secured by screws in four deep insets in the bottom which pass through the body and screw directly into the lid. On my projector, one of them had been covered with a Quality Inspector's sticker. I also removed three other small screws from the bottom that may have attached to the heat sink. The screws under the lens definitely do not need to come out. The lid on the projector did not have any snap-together clips.
Once the lid is out of the way, you should see what the picture shows - the circuit board.
Three screws hold it down, IIRC. You will need to disconnect the tiny ribbon cable from the top rear edge but, DO NOT SIMPLY PULL! Pulling out the cable could damage it - I've done it before on other devices.To release the cable there is a small lever or clip (I don't remember what its called but it's the little dark bit on the white female port) just pop it up with a fingernail or something that won't damage the cable.
There are several power connectors that need to be removed from the bottom. Gently lift the board, then pull the plug out with your fingernails or some hobby pliers. These connectors can be fragile so don't pull on the wires. It may be wise to mark which connector goes to which port, just in case.
Step 2: Let's Practice Rocket Surgery!
No rockets were harmed in the making of this 'ible.
With the 'lid' off and the circuit board free, it's time to disassemble the lamp.
Observe the orientation of the bracket, then unscrew the lens bracket and set the bracket and lens aside.
Next, Unscrew the LED bracket from the heatsink. Again, look at how the parts go together, maybe take a pic. It's deceptively simple.
Alright, we've opened it up - now for the transplant.
Heat your soldering instrument up and tin the tip as appropriate.
Then proceed to the next step!
Step 3: Any Transplant That You Can Walk Away From...
First, mark the two wires connected to the LED so you don't mix them up.
De-solder the wires.
As you perform the next step, take note of the markings on the lamp - they indicate how to orientate the new lamp. Pull the old white light LED out of the bracket. The legs of the LED are shaped in such away that they prevent easy extraction of the LED. Go ahead, yank it out. That little lamp might make a nice flahlight bulb.
To install the new lamp into the bracket you will need to bend the leads up and probably curl them in a little. Maybe not, but that's what I had to do to get mine to fit correctly. It's important to get the LED installed correctly so that the metal backing can have maximum contact with the heat sink.
You'v completed the hard part.
Next step, reassembly!
Step 4: No Pictures This Time.
Putting the projector back together wasn't hard but just for reference I've listed the steps anyway.
When dealing with wires try to keep them out of the way of the light path and cooling fan. You may have noticed but at some key points the cables have guides designed into the body of the machine to help keep them where the need to be and away from the burning death of things like electrical shorts.
- Re-solder wires to LED - be sure they are right so we don't toast something.
- Apply heat-sink thermal goo to the back of the LED and then screw it onto the heatsink
- Secure the lens with the lens bracket to the LED and heatsink and then pup them back into place.
- Reinstall the black plastic shield. Did I forget to mention that earlier? I used three screws on the shield I think, but I had an extra screw when I was done so I must've missed one.
- Re-attach the power lines to the circuitboard and then screw it down. Three more screws here I think. Note that the screws for the board go in the little holes. The large holes is where screws that hold the shell together pass through.
- Install the ribbon cable by sliding it in until it looks to be evenly centered then push the 'tab' thing down until it snaps into place.
- Put the lid on and flip it over. Install the four screws in the deep insets.
That should do it!
Step 5: The Burn Test
Hopefully no flames will be involved but it would be smart have an extinguisher handy anyway.
I don't yet know whether we might have needed to remove some of the crystal and such but when I tested my projector I could faintly see a little light projected on the wall, so I know it was working to some degree. However, when I pointed my digital camera at the projecting lens, I could see the output was quite bright.
If you don't have any resin to cure yet, you can at least see if the lamp is working but using an un-shielded or low-shielded digital camera to inspect. Most digital cameras are or should be shielded against UV light making the projector appear dark but some, like the camera on my phone have no problem seeing in UV. To check it out, point a remote that uses a diode in the end at you digital camera. Then press and hold a button on the remote while you look at the received image, you should see a bright purple light onscreen. Tada! You've done it!
Please, do NOT try to look directly into he projector's output path or you may end up damaging your vision.
Step 6: Semi-Conclusion
I plan to test this printer with printing a visible spectrum light curing resin. I'm currently looking at H-NU 470 photoinitiated resins. They're not cheap but I'm really hoping to find a supplier of the PI and co-initiators that will sell them in an unmixed format so that I can test, store and maybe even distribute. If I come up with a good solution it'll probably go into this 'ible.
As I finish my SLA printer I'll plan on updating the 'ible with more details and I''l put up a separate one for the printer itself.
Thanks for reading and I hope this instructible has been a help to you!